stm32f4

8.2.19. stm32f4#

8.2.19.1. Supported Hardware#

The BSP is known to work on the following boards:

Board	Notes
STM32F411 Black Pill (WeAct)	USB-C port wired to DWC2 USB OTG FS peripheral
NUCLEO-F401RE	On-board ST-Link; ST-Link USB is virtual COM port only
NUCLEO-F446RE	On-board ST-Link; ST-Link USB is virtual COM port only
STM32F407VG Discovery	On-board ST-Link V2

8.2.19.2. Clock Driver#

The clock driver uses the ARMv7-M SysTick peripheral. The STM32F411 runs at up to 100 MHz and the STM32F407 at up to 168 MHz. Clock configuration is in bsps/arm/stm32f4/start/bspstart.c.

8.2.19.3. Console Driver#

The console uses a UART configured in the BSP.

On Nucleo boards the ST-Link virtual COM port connects to USART2 (PA2/PA3) at 115200 baud. The board appears as /dev/ttyACM0 on Linux.

On the STM32F411 Black Pill the console is on USART1 (PA9 TX, PA10 RX) at 115200 baud, 8N1. A USB-to-UART adapter connected to those pins is required to read console output. The USB-C port on the Black Pill connects to the DWC2 USB OTG peripheral (PA11/PA12) and does not provide a serial console.

8.2.19.4. How to Run an RTEMS Application on the Board#

By following these simple steps, you can deploy your RTEMS application on the board. These steps include:

Building your RTEMS Application, already discussed in the Build Your Application.
Flashing the application onto your board using either OpenOCD or stlink tools.
Viewing the serial output over UART.

8.2.19.5. Flashing with OpenOCD (Nucleo Boards)#

This method uses OpenOCD and works well with Nucleo boards where the on-board ST-Link exposes a GDB server.

Download and install OpenOCD for your host operating system.

Start OpenOCD using the configuration file for your board:

openocd -f board/st_nucleo_f4.cfg

Upon a successful connection you will see output similar to this:

Open On-Chip Debugger 0.12.0
...
Info : [stm32f4x.cpu] Cortex-M4 r0p1 processor detected
Info : starting gdb server for stm32f4x.cpu on 3333
Info : Listening on port 3333 for gdb connections

Open another terminal and launch GDB with your compiled application:

arm-rtems7-gdb path/to/your/compiled/application

Connect to the OpenOCD GDB server, load, and run:

(gdb) target remote :3333
(gdb) load
(gdb) cont

8.2.19.6. Flashing with stlink Tools (All Boards)#

The open-source stlink tools work with both Nucleo boards and the STM32F411 Black Pill without requiring OpenOCD.

Install on Ubuntu or Debian:

sudo apt install stlink-tools

Verify the programmer is detected after connecting via USB:

st-info --probe

Expected output for an STM32F411:

Found 1 stlink programmers
  version:    V2J45S7
  flash:      524288 (pagesize: 16384)
  sram:       131072
  chipid:     0x0431
  descr:      F411xC/E

If the output shows Found 0 stlink programmers, check that the USB cable carries data (not power only) and install the udev rules:

sudo cp /usr/share/doc/stlink-tools/49-stlink.rules /etc/udev/rules.d/
sudo udevadm control --reload-rules

Unplug and reconnect the ST-Link, then retry st-info --probe.

Convert the ELF executable to a flat binary and flash it:

arm-rtems7-objcopy build/arm/stm32f4/testsuites/samples/hello.exe hello.bin
st-flash write hello.bin 0x8000000

A successful flash ends with:

INFO common.c: Flash written and verified! jolly good!

If the board does not respond to flashing, try the reset variant:

st-flash --connect-under-reset write hello.bin 0x8000000

To debug with GDB using stlink tools, open two terminals.

Terminal 1 — start the GDB server:

st-util

Terminal 2 — connect GDB:

arm-rtems7-gdb build/arm/stm32f4/testsuites/samples/hello.exe

Inside GDB:

(gdb) target extended-remote :4242
(gdb) load
(gdb) cont

8.2.19.7. Serial Monitor Output#

Important

The correct serial device depends on your board. Nucleo boards appear as /dev/ttyACM0 (ST-Link virtual COM port). The STM32F411 Black Pill requires a USB-to-UART adapter on PA9 (TX) and PA10 (RX), which typically appears as /dev/ttyUSB0.

Make sure your board is connected and minicom is installed:

sudo apt install minicom

Open the minicom configuration menu:

sudo minicom -s

Go into Serial port setup and press a to select Serial Device.
Change the device to /dev/ttyACM0 (Nucleo) or /dev/ttyUSB0 (Black Pill with USB-UART adapter) and press Enter.
Press f to change hardware flow control from Yes to No.
Scroll to Exit and press Enter.

Press the reset button on your board. Example output:

*** BEGIN OF TEST HELLO WORLD ***
*** TEST VERSION: 7.0.0.a413333f2f04130e82e15addba402887222c345f
*** TEST STATE: EXPECTED_PASS
Hello World
*** END OF TEST HELLO WORLD ***

[ RTEMS shutdown ]
RTEMS version: 7.0.0.a413333f2f04130e82e15addba402887222c345f
RTEMS tools: 15.2.0 20250808 (RTEMS 7, ...)
executing thread ID: 0x0a010001
executing thread name: UI1

8.2.19.8. Known Limitations#

No user USB connector on Nucleo boards: The NUCLEO-F401RE and NUCLEO-F446RE connect the STM32 USB OTG pins (PA11, PA12) to the chip but do not expose them on a USB connector. The only USB port on those boards is the ST-Link port, which handles programming and the virtual COM port only. For USB peripheral development or TinyUSB testing, use the STM32F411 Black Pill, which has a USB-C connector wired to PA11/PA12 via the internal DWC2 Full Speed peripheral.

No USB-to-serial bridge on Black Pill: The STM32F411 Black Pill USB-C port connects directly to the DWC2 USB OTG peripheral, not to a serial bridge. Console output requires a separate USB-to-UART adapter (CP2102 or CH340) on PA9 and PA10.

Black Pill BOOT0 recovery: If the board enters the ROM bootloader and does not respond to st-flash, hold BOOT0, press and release NRST, wait one second, release BOOT0, then retry the flash command.

8.2.19.9. Memory Map#

Region	Start address	Size
Flash	`0x08000000`	512 KB (F411), 1 MB (F446), 1 MB (F407VG)
SRAM	`0x20000000`	128 KB (F411), 128 KB (F446), 192 KB (F407VG)

Measured footprint of RTEMS hello world on STM32F411 (arm/stm32f4 BSP, GCC 15.2.0):

Section	Size
Flash (.text + .rodata + .data load)	~75 KB
RAM (.data + .bss)	~6.5 KB

8.2.19.10. USB Support#

The STM32F4 contains a Synopsys DWC2 USB OTG Full Speed peripheral (USB_OTG_FS on PA11/PA12). This peripheral is supported by TinyUSB via the dwc2 driver. Porting TinyUSB to RTEMS with the STM32F411 Black Pill as the reference hardware platform is tracked in .